1. Field of the Invention
The present invention relates to an electron emission device, and in particular, to an electron emission device and a method of manufacturing the same which enhances the structure of a focusing electrode for controlling the electron beams and an insulating layer for supporting the focusing electrode.
2. Description of Related Art
Generally, electron emission devices are classified into a first type where a hot cathode is used as an electron emission source, and a second type where a cold cathode is used as the electron emission source.
Cold cathode electron emission devices include, for example, field emitter array (FEA) devices, surface conduction emitter (SCE) devices, metal-insulator-metal (MIM) devices, metal-insulator-semiconductor (MIS) devices, and ballistic electron surface emitting (BSE) devices.
Electron emission devices vary in their structure depending upon the specific type of the device. However, most have a basic structure including a vacuum chamber formed by two substrates, electron emission regions and driving electrodes that are formed on one of the substrates, and phosphor layers that are formed on the other substrate. The driving electrodes help emit electrons from the electron emission regions and phosphor layers emit light to display the desired images.
In an electron emission device with the above general structure, correcting the trajectory of electron beams to enhance the display characteristics has been a challenge. For example, electrons emitted from the electron emission regions on one of the substrates may diffuse before colliding against the phosphor layers on the other substrate. As a result, the diffused electrons do not strike the intended phosphor layers; instead, they land on other-neighboring phosphor layers causing them to emit an unintended color.
Metallic mesh-shaped grid electrodes or focusing electrodes have been used to control the trajectory of the electron beams. A grid electrode is placed between the two substrates while set apart from them using spacers. Focusing electrodes are located over the first substrate, which includes the electron emission regions, and surround the electron emission regions.
Fabrication of electron emission devices using grid electrodes involves difficult and complicated processing steps. At first, spacers are mounted on one of the two substrates; then, the grid electrode is aligned to the substrates; and then, the substrates are attached to each other to form a vacuum chamber.
Effective use of focusing electrodes may also lead to difficulty in the required fabrication process. The electron beam focusing effect of a focusing electrode is enhanced if the focusing electrode is set at a distance from the electron emission regions. To set the focusing electrode away from the electron emission regions, the thickness of the insulating layer, that supports the focusing electrode, must increase. An increased insulator thickness, in turn, results in longer and deeper opening portions, passage wells or holes through the insulator layer to the electron emission regions on the substrate. Forming holes with a high vertical to horizontal ratio involves fabrication processing difficulties. For example, if a wet etch process is used to form a hole, the etchant may tend to widen the hole as it deepens it. Therefore, achieving a deep hole while keeping the width small is not trivial.